(1) Field of the Invention
The present invention relates to a polymer binder for a dry toner to be used for the development stage in an electrophotographical process, a process for the preparation of this polymer binder, and a toner composition.
(2) Description of the Related Art
Many binder resins for dry toners have been proposed and various toner characteristics have been improved. However, large quantities of monomers are left in conventional binder resins for toners or in conventional toners, and unpleasant smells are generated in the toner-preparing process, especially at the melt-kneading steps, to worsen the working environment. Furthermore, a bad smell is generated at the copying operation to give an unpleasant feeling to the operator. There is a strong demand that these drawbacks be eliminated.
Under this background, and in order to solve this problem, the present inventors tried a method in which the polymerization product is maintained at the polymerization temperature or a higher temperature for a long time after termination of the polymerization, and a method in which, after termination of the polymerization, a solid resin obtained by dehydration and drying is treated in the molten state by an extruder or the like to remove the residual monomer. However, these methods have problems in that the amount of the residual monomer cannot be reduced to a satisfactory level, a long time is required for heating, the process becomes complicated, and the cost is increased.